A filter bag for products to be infused, such as tea, camomile and the like, and a method of producing this filter bag are described in my copending application Ser. No. 199,682.
This filter bag is essentially constituted by folding a piece of filter paper, provided on one of its surfaces with a light coating of thermoplastic material, along a median line in such a way as to form two symmetrical half sections having the thermoplastic coating on its internal surfaces facing one another and by joining the two half sections by heating along their respective edges, so as to create the space for containing the product to be infused.
A suspension thread of natural fiber having a label attached to it can be applied to a filter bag by heating the areas of the filter paper corresponding to the natural fiber thread at the opposite sides of the label disposed on one external face of the bag in which the natural fiber thread is folded parallel to itself in order to be wound around the bag to overlie the other surface, and at one area at least of this latter face and at the edges of the said two half sections of one side of the bag between which the terminal portion of the said natural fiber thread is inserted causing a localized impregnation of the natural fiber thread with the thermoplastic material of the coating layer inside the bag and which diffuses through the filter paper following this heating operation.
The connection of the natural fiber thread to the filter paper bag obtained in this way is sufficiently stable to ensure that the bag may be handled without problems during all the subsequent steps for treating the bag until it is packed in containers for sale to the consumer, the tag may be readily drawn away from the bag at the time of use by the consumer without causing any damage or tearing of the filter paper of the bag.